PARENT SESSION
Oral Session #36: Conservation of aquatic systems: Ecology and ecotoxicology. Presiding: R. Lathrop.
Tuesday, August 7, 2001. 1:00 PM to 5:15 PM. Hall of Ideas H.
River flow regime as a restoration target:assessing flow alteration in rivers of the Great Lakes Basin.
Allan, David1, Hinz, Leon1, 1
ABSTRACT- Rivers of the Great Lakes Basin have experienced significant alteration of their flow regimes, affecting biotic assemblages and entire ecosystems. We examined the magnitude, frequency, duration, timing, and rate of change of flow at USGS gages using the Indicators of Hydrologic Alteration (IHA) software. The entire period of record, as well as the earliest and most recent 20-years, were compared. Flow regimes changed markedly over the 20th century, based on 123 gages in Michigan. Flow magnitude increased, fewer low-flow events occurred and were of shorter duration, flow predictability increased, and the frequency of high flow events increased. Dams clearly have regulated river flow in some instances, increasing predictability; whereas changing land use is hypothesized to be responsible for enhancement of high-flow extremes. Because the historic gage record is insufficient to establish pre-disturbance flow regimes, historic flows are estimated using predictive models based on landscape variables to back cast flow using pre-settlement landscape variables. In Michigan, where pre-settlement maps are available this approach appears to hold great promise. Final results of this project will include a GIS product, including mapped gages with hydrologic information, dams with attributes, and biological information, to facilitate information transfer to local government and watershed organizations.
KEY WORDS: river, flow regime, restoration, hydrology